A Saudi-led coalition fighting Yemen's Houthis said it intercepted and destroyed six ballistic missiles fired by the group, the Saudi state news agency SPA reported on Sunday. No damage or casualties were reported.

Earlier, a military spokesman for the rebel Houthi movement said the group fired 10 Badr-1 ballistic missiles at Saudi Arabia's southwestern Jizan airport, killing and wounding dozens, Reuters reported.

The attack is part of an escalation of cross-border assaults in the four-year-old conflict between the Houthis and coalition forces.

Earlier on Sunday, the coalition said it shot down a Houthi drone fired towards the southern city of Khamis Mushait, site of a major military base, AFP reported.

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The Houthis, who control the capital Sanaa, have in the past few months stepped up their attacks against targets in the kingdom. In response, the coalition has targeted military sites belonging to the group, especially around Sanaa.

"The Houthi militias’ continued targeting of civilians through drones and ballistic missiles is an act of aggression and terrorism and a war crime according to international human law," the coalition spokesman, Colonel Turki al-Malki, said in a statement.

The western-backed coalition led by Saudi Arabia and the UAE intervened in Yemen in 2015 to try to restore the internationally recognised Yemeni government that was ousted from power in Sanaa by the Houthis in late 2014.

The escalation of violence threatens a UN-sponsored deal for a ceasefire and troop withdrawal from Hodeidah, which became the focus of the war last year when the coalition tried to seize the port, the Houthis’ main supply line and a lifeline for millions of Yemenis.

The conflict has killed tens of thousands of people, many of them civilians, relief agencies say.

It has also triggered what the UN describes as the world's worst humanitarian crisis.